Hollow exercise ball



FIG. 1 is a front view of a hollow exercise ball showing my new design;

FIG. 2 is a top view of the hollow exercise ball;

FIG. 3 is a bottom view of the hollow exercise ball;

FIG. 4 is a cross-sectional view of the hollow exercise ball;

FIG. 5 is a second cross-sectional view of the hollow exercise ball; and,

FIG. 6 is a front view of the hollow exercise ball as used.

Right side view, left side view and rear view not shown are mirror images of the front view. Any broken lines illustrative of environmental structure in the drawings are not part of the design sought to be patented. 

CLAIM The ornamental design for a hollow exercise ball, as shown and described. 